Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 230500
AFDRIW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RIVERTON WY
1100 PM MDT SAT AUG 22 2015

.SHORT TERM...TONIGHT THROUGH SUNDAY (ISSUED AT 337 PM MDT)

THE SOUTHWEST BOUND COLD FRONT HAS GOTTEN HUNG UP ALONG THE
CONTINENTAL DIVIDE. SMOKE AND NORTHEAST WINDS ALONG WITH COOL
TEMPERATURES HAVE BEEN THE RULE EAST OF THE DIVIDE TODAY AS SMOKE
POURS IN FROM MONTANA AND GETS TRAPPED WITHIN THE FRONTAL
INVERSION. CONDITIONS HAVE BEEN ESPECIALLY CHILLY IN NORTHERN
JOHNSON COUNTY WHERE TEMPERATURES HAVE REMAINED IN THE UPPER 50S
THIS AFTERNOON ALONG WITH STRONG POST FRONTAL NORTH WINDS OF OVER
50 MPH AT THE BUFFALO AIRPORT WHERE WINDS CONTINUE TO HOWL. THE
LOW CLOUDS THAT INITIALLY ACCOMPANIED THE FRONT ALONG AND EAST OF
THE BIG HORN MTNS AND CASPER ARCH...ALONG THE OWL CREEK MTNS AND
ALONG AND JUST NORTH OF THE GREEN MTNS HAVE DIMINISHED. THESE
LOW CLOUDS WENT UNNOTICED UNLESS ONE WAS DIRECTLY UNDERNEATH THEN
THANKS TO THE SMOKE. IN THE MEANTIME...SOUTHWEST OF THE
FRONT...BRISK WEST WINDS ALONG WITH AN RH IN THE LOW TO MID TEENS
WERE PREVALENT ACROSS SWEETWATER...SOUTHERN LINCOLN AND UINTA
COUNTY FOR THE SECOND DAY IN A ROW WHERE THE RED FLAG WARNING WILL
RIDE THROUGH 8 PM. THE FRONT WILL EVENTUALLY OVERTAKE MOST OF THE
CWA BY MID TO LATE EVENING TONIGHT AS WINDS VEER TO THE EAST
NORTHEAST ACROSS SWEETWATER COUNTY. ANY LINGERING CLOUDS WILL
DISSIPATE THIS EVENING AS POST EXITING TROUGH STRONG SUBSIDENCE
AND CONFLUENT UPPER FLOW CONTINUES. WITH CLEARING SKIES AND COOLER
AIR SETTLING IN BEHIND THE FRONT...EXPECT A CHILLY NIGHT TONIGHT
AND EARLY SUNDAY MORNING WITH TEMPS APPROACHING OR A LITTLE BELOW
FREEZING IN THE FAR WEST VALLEYS AND BASINS AND 30S COMMON AT THE
LOWER ELEVATIONS EAST OF THE DIVIDE. ON SUNDAY...WARM AIR
ADVECTION WILL TAKE OVER AS THE JET STREAM QUICKLY SHIFTS BACK
NORTH OF THE AREA WITH A WARMER AND DRY DAY IN STORE. THERE WILL
BE SOME AFTERNOON CLOUDS AND PERHAPS A STRAY SHOWER OVER THE
HIGHEST PEAKS AS AN UPPER LEVEL DISTURBANCE TRACKS EAST NORTHEAST
FROM NORTHERN CALIFORNIA.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY

WEAK DISTURBANCE OVER NRN CA LOOKS TO GET CAUGHT IN THE FLOW AND
MOVE TOWARDS WRN WYO AT THE BEGINNING OF THIS PERIOD WHILE THE
OVERALL HEIGHTS START TO REBUILD ALLOWING SOME MINIMAL MID LEVEL
MOISTURE TO EDGE INTO OUR SWRN ZONES. FLOW DIRECTION OFF THE UINTAS
LOOKS LIKE IT WILL BE W TO WNW BUT CLOSE ENOUGH TO ADD SOME ISOLD
EVENING STORMS IN THE FAR SWRN CORNER OF SWEETWATER SUNDAY EVENING.
OTHERWISE...ANOTHER WEAK RIPPLE MIGHT MOVE INTO THE WEST WITH JUST A
LITTLE MORE MID LEVEL MOISTURE ROTATING AROUND OUR 4-CORNERS HIGH
RESULTING IN ISOLATED MTN TSTMS WITH A FEW GUSTY STORMS TRYING TO
COME OFF THE MOUNTAINS MONDAY EVENING IN W-NW FLOW. NOT A LOT OF
CHANGE TUESDAY WITH MAYBE JUST A LITTLE MORE MID LEVEL MOISTURE
EDGING INTO THE FAR SOUTH IN SW FLOW DOWN THERE. IDEA OF ISOLD
STORMS IN SWEETWATER COUNTY IS REASONABLE AND WILL LEAVE THOSE IN
THERE. ON WEDNESDAY...WE ARE STILL WATCHING FOR A POTENTIALLY
SIGNIFICANT SHORTWAVE TO COME OUT OF OUR TSTM MASS IN NRN MEXICO AND
MOVE INTO SWRN WYO BY 00Z THURSDAY AND THEN MOVING SLOWLY EWD INTO
THURSDAY. MUCH BETTER CHANCE OF SHOWERS/TSTMS IN THE SW WITH THIS
PATTERN. GFS IS ALSO BULLISH ON THE LOW LEVEL MOISTURE SURGE...MUCH
MORE SO THAN THE NAM OR ECMWF. WE WILL NEED TO WATCH THIS BECAUSE
THERE WOULD LIKELY BE A DECENT LOWER LEVEL MOISTURE SURGE IF THIS
SHORTWAVE COMES STRAIGHT UP FROM THE SOUTH. SHOWERS/TSTMS WILL
LIKELY CONTINUE OVERNIGHT ALONG THE TRACK OF THIS SHORTWAVE IN THE
SOUTH WITH THE CIRCULATION POSSIBLE BEING CLOSE ENOUGH EVEN THURSDAY
AFTERNOON FOR SOME CONCENTRATED STORMS IN OUR ERN ZONES. SOME
DISCREPANCY ON UPPER HIGH POSITION BY FRIDAY INTO SATURDAY BUT
LEANING TOWARDS A GENERAL 4-CORNERS POSITION WHICH WILL LEAVE OUR
AREA OPEN TO SHORTWAVES AND SURGES OF MOISTURE FROM THE DESERT SW.

&&

.AVIATION.../06Z ISSUANCE/

VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. THERE WILL BE AREAS
OF SMOKE THAT WILL REDUCE VISIBILITY TO MVFR VALUES THROUGH 18Z
SUNDAY. MOUNTAINS MAY BE PARTIALLY OBSCURED BY SMOKE AS WELL. THE
SMOKE WILL DISPERSE FOR THE MOST PART SUNDAY AFTERNOON WITH VFR
VISIBILITY PREVAILING.

&&

.FIRE WEATHER...

SUNDAY WILL BE DRY OVER THE REGION WITH LIGHT WIND. AFTERNOON
RELATIVE HUMIDITY WILL DROP IN MANY LOCATIONS TO UNDER 15 PERCENT
SUNDAY AFTERNOON BUT WIND SPEEDS WILL BE LIGHT. ISOLATED AFTERNOON
AND EVENING THUNDERSTORMS WILL DOT THE WESTERN MOUNTAINS AND VALLEYS
MONDAY AFTERNOON.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...LIPSON
LONG TERM...SKRBAC
AVIATION...AR
FIRE WEATHER...AR


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